Role of FGF-8 in bone formation during orofacial development of the chicken embryo *
FGF-8, a member of the fibroblast growth factor（FGF）family, plays a key role in development of the hindbrain and limbs, and is also expressed in the developing face. The expression pattern of FGF-8 and its function were examined in the chick embryo. FGF-8 is expressed in epithelial cells of the nasal fossa, and of the side edges of the lower and upper jaws in normal embryos. When FGF-8 was misexpressed with the retrovirus vector at stage 20 in the maxillary prominence, the upper jaw curved to the side of misexpression without change in facial width. Loss or hypoplasia of palatine bone, maxillary bone, and jugal was frequently observed. Loss or hypoplasia of cartilage elements was not observed, but ectopic cartilage did form in the upper jaw. FGF-8 has no effect on soft tissue organization. These results suggest that FGF-8 plays a key role in craniofacial morphogenesis, and that excessive FGF-8 expression promotes cartilage differentiation, which in turn, results in suppression of bone formation during orofacial development.(Accepted on October ７，2005)
